Andy, I've checked visual sitemap saving on a several big website projects, but could not reproduce the message. What is the site you're trying to save the visual sitemap of? What's the image format - PNG, JPG, etc.?

Andy, I could not reproduce this message, but it looks like visual sitemap of the website is too big to generate. It consists of 1273 pages and at least 79241 links (without images, CSS, JS, etc.) Its size would be 2540 x 132821 pixels, so it would be totally unrepresentative in any case. In order to visualize the site, I'd recommend you to exclude some of the website's directories (such as /utilities/, /calendar/, /Music_MU/, /templates/), if it's possible.

P.S. Please also exclude URLs containing 'thisdate' substring, since the crawling process goes to infinite - the app tries to crawl every page regarding to its day at the calendar. 'viewevent' substring or 'EventID' parameter could be excluded also.